Artificial laminated carious lesions were made on the buccal surface of human premolars. The volume percentage of mineral was determined as a function of depth by microradiography. Using the electron microprobe, the signals for Ca, Na, Mg, P and Cl were recorded as a function of depth both through the lesions and through the adjacent sound enamel. In the demineralized parts of the lesions there was a preferential loss of Na and a preferential retention of Cl. In the surface layers and the laminations the Na/Ca and Cl/Ca ratios were practically the same as in the adjacent sound enamel. This indicates that these surface layers and laminations were not formed by gross dissolution of the original mineral followed by gross precipitation of another, less soluble calcium phosphate, but that they remained there during the continuous demineralization due to the fact that the microcrystals became resistant to dissolution, perhaps due to protection by a thin layer of precipitated fluorapatite or fluoridated hydroxyapatite. In a previous study the same was found for surface layers and laminations in natural laminated carious lesions. This indicates that during continuous in vitro demineralization tooth enamel mineral behaves similarly as during intermittent in vivo demineralization.